In consideration of the need to display commercial merchandise, to facilitate stock management in workshops or on warehouse commodity rack or shelf assemblies, racks and shelves have become indispensable which are easy to set up for use and which permit modification into various shapes and volumetric changes, if and when necessary, which are strong enough to support loads of given dimensions and weights. Such racks should be laid out in a pleasing manner so as to help to stimulate the desire to purchase items therefrom on the part of window-shoppers or passers-by.
It is well known that when a multitude of display shelves are assembled, differing in kinds and brands, those composed of two-way or three-way joints assembled with rectangular metal tubes, have often been found to lack the fit and precision required by the joints, which in turn is responsible for failure to meet rigid standards as regards compression strength. This renders the structures restricted in their scope of application.
FIG. 1 is an illustration of a prior art shelf joint. Joints or adaptors structured as such for use to form a commodity shelf or stand have been found to have the following shortcomings:
(1) the necessity to adjust the respective shaft arms of the joint separately, causing much waste of time and labor, and discouraging attempts to install the shelf;
(2) loosening of matching pieces as a result of frequent alteration of the loads stacked on the shelves, causing concerns for safety;
(3) loosening of the shelf by displacement also having concern for safety;
(4) unstable rocking of the shelf after several times use due to injury to the screw threads owing to strong torsion brought about by the dismantling and reassembling of the shelves.
Another type of joint for use with a commodity shelf having an outer diameter that is smaller than the inner diameter of the shelf tubework by a very minimal dimension can very often bring about injury while being coupled, there being a lack of any fastening of the fittings, and cause a falling of the finished shelf much more likely than with other types of joints.